(1) Field of the Invention
The present invention relates to a metal-ceramic composite body and a method of manufacturing the same.
(2) Description of the Prior Art
Since ceramics such as zirconia, silicon nitride, silicon carbide and the like are excellent in the mechanical strength, thermal resistance and wear resistance, these ceramics are now being noted as high temperature structural materials such as gas turbine engine parts, diesel engine parts and so on, and wear resistant materials. However, because ceramics are generally hard and brittle, they are inferior to metals in formability and workability. Further, it is difficult to form mechanical parts such as engine parts from the ceramic material alone due to its poor toughness. Therefore, the ceramic materials are generally used in a form of the composite structural body in which a metallic member and a ceramic member are bonded together.
Methods in which the metallic member and the ceramic member of the metal-ceramic composite body used as engine parts are mechanically bonded together, there are include, for instance, a structure in which a rotary shaft 1 of a ceramic turbine wheel and a rotary shaft 2 of a metal compressor wheel are bonded together by shrinkage fitting a metallic cylindrical collar 21 around the outer periphery thereof as shown in FIG. 1 (Japanese Patent Laid-Open No. 200,601/1982) and a structure in which a rotary shaft 4 of a turbine wheel made of ceramics is fitted into a recessed portion 3 formed at the end portion of a rotary shaft 2 of a metal compressor wheel (U.S. Pat. No. 3,666,302).
However, these conventional bonding structures have the following defects:
(1) Since the thickness of the metallic member at the bonding portion is large, a large stress concentration occurs at a portion of the ceramic member at which the ceramic member is inserted into the metallic member. That is, in the case of the metal-ceramic composite body having a conventional bonding structure, as shown in FIG. 1, since the outer diameter of the composite body changes at an edge 5 of the metal collar 21 to result in a discontinuous change in rigidity, when a tensile load or a bending load is applied to the composite body, the stress concentrates in the portion of the ceramic member near the edge of the metal collar, and fracture initiates from this portion. PA0 (2) In the case of the conventional bonding structure as shown in FIG. 1, since a space l.sub.1 between the back surface 6 of the large diameter portion of the ceramic member and the edge surface 5 of the metallic member is small, when a bending load is applied onto the bonding portion, the stress is concentrated upon the ceramic member at the space l.sub.1, so that fracture occurs from this portion.
Similar defects are apparent in the embodiment shown in FIG. 2.